This invention relates to a method for manufacturing a unit piece of a V pulley, and more particularly to a method for manufacturing a unit piece a pair of which are assembled in back-to-back relation into a single complete V pulley which is well adapted for use in a small-sized rotary machine.
It has been a common practice in manufacturing a V pulley for use such as in a vehicle electric charging generator to machine a cast-iron block or steel block to a desired shape. In case of the cast-iron, a metal stock is melted under heat for casting the same into a cast mold, so that such a method surffers from an increasing amount of material expenses, heat and light expenses and expenses for man power which are all required for melting and casting the material. In addition, the machining cost required for cutting the casting to desired accuracy by a device such as lathe is increased, with the accompanying increase in energy required for melting the metal stock as well as in energy required for machining the casting, thus resulting in considerable disadvantages.
On the other hand, there is known a steelplate pulley which is manufactured by subjecting a circular steel-plate having a thickness T to drawing to thereby provide a pulley unit piece of a dish form. However, such an attempt is also confronted by shortcomings in that, since the thickness of the pulley unit piece is uniformly equal to the aforesaid thickness, the weight of the assembled pulley is considerable and the pulley, when in use, produces resonance with the vibration in a rotary machine, and in that since the thickness T is relatively large, there has been increased the inertia of the pulley. Those shortcomings are apparently undesirable from every viewpoint in a pulley.